Between 2003 and 2009, there were 395 "potential release events" and 66 "potential loss events" in American labs involving select agents, a category that includes many of the most lethal bacteria and viruses, including anthrax.

The circumstances of the recent anthrax incident suggest more reason for concern: The workers exposed were not those in the high-containment labs. Based on current reports, the problem arose when anthrax -- incorrectly thought to be dead -- was removed from the high-containment lab and exposed people who had no knowledge that they were in contact with live bacteria.